The invention relates to a method and a device for producing an energy-absorbing profile for a motor vehicle. Such an energy-absorbing profile includes an extruded hollow profile with outer walls and at least one inner wall, which connects two outer walls. In case of an accident, the energy-absorbing profile absorbs energy by deformation within the profile.
Parts of vehicle structures that are configured as deformation zones serve for the passive protection of vehicle occupants as well as for protection of the supporting structure of the motor vehicle. The goal is to absorb energy resulting from an impact and convert it into deformation energy in the energy-absorbing profile. This is intended to reduce the forces acting on vehicle occupants and pedestrians involved in the accident and also to prevent exceeding critical load levels at which support structures of the motor vehicle may suffer permanent damage.
Energy-absorbing profiles can be configured for example as crash boxes, which in combination with the bumper cross member adsorb the collision forces in case of an impact at low speed without causing damage to the remaining portions of the vehicle body structure. A crash box formed from extruded profiles, which are nested within each other, is state of the art through DE 10 2011 107 698 A1.
A crash box for motor vehicles for absorbing energy in case of a collision of the motor vehicle with an obstacle is also described in US 2002/0158 384 A1. The crash box has a hollow cylindrical body, which is made of metal and defines a longitudinal direction of the bumper, and has deformation embossments in the sheath. The deformation embossments serve for achieving a defined compression of the hollow body when impinged with a force in longitudinal direction.
DE 102 34 253 B3 discloses a method for producing a crash box for motor vehicles from a semi-finished sheet metal and a crash box for motor vehicles with a multi-chamber profile. For producing the crash box the semi-finished sheet metal is formed into a multi-chamber profile, in particular a double-chamber profile, by bending or folding.
Cross members or longitudinal members can also be configured as energy-absorbing profile. This applies in particular to cross members and longitudinal members, which are exposed to an axial load in case of a collision.
From a manufacturing point of view as wells as due to the energy-absorbing capacity and for reasons of weight reduction, energy-absorbing profiles made of extruded hollow profiles made from light metal materials are used. In this context, a bumper with energy-absorbing profiles arranged thereon in the form of deformation elements is state of the art through DE 10 2008 029 634 A1. The deformation elements are rectangular hollow profiles with one or multiple chambers. A multi-chamber profile is formed by inner walls, which are arranged between two outer walls and connect the outer walls.
The bumper for motor vehicles described in DE 196 03 053 C1 has a first extruded hollow profile part whose profile extends transverse to the longitudinal axis of the bumper. For increasing the buckling stiffness of the bumper, the first extruded hollow profile is form fittingly surrounded by a sleeve-shaped second hollow profile part, wherein the open ends of the hollow profile part are supported on one side on a flange part of the bumper and on the other side on the cross member of the motor vehicle.
The advantages of the extruded profiles include the possibility to be able to also produce complicated shapes of hollow profiles. However, the cross-sectional geometry and the outer and inner shape of the extruded strand is defined by the pressing tool and manufacturing is the same over the entire length of the hollow profile.
In energy-absorbing profiles for motor vehicles made of extruded hollow profiles, the inner walls between two outer walls serve in particular for providing the profile with stability and to contribute to energy-absorption. In this regard it is desirable to configure the deformation properties of the energy-absorbing profile specific for the particular component in order to influence the deformation property and with this the energy-absorbing capacity.